N-alkyl-phosphoro-amido-thioates

ABSTRACT

N-alkyl-phosphoro-amido-thioates, i.e. O-(2-nitrophenyl)-Oalkyl-N-alkyl-phosphoro-amido-thioates or O-(2-nitrophenyl)-Oalkyl-N-alkyl-amido-thionophosphates, which possess herbicidal properties and which may be produced by conventional methods.

United States Patent [1 1 Schrader et al.

( 1 Sept. 18, 1973 l N-ALKYL-PHOSPHORO-AMlDO-THIOATES (75] inventors: Gerhard Schrader,

Wuppertal-Cronenberg; Ludwig Eue; Helmuth Hack, both of Cologne, all of Germany; Seiichi Hirane; Masahiro Aya, Shigeo Kishino; Nobuo Fukazawa, all of TokyoJapan [73] Assignee: Bayer Aktlengesellschait,

Leverkusen, Germany 221 Filed: Feb. 9, 1970 [2]] Appl. No.: 10,026

[30] Foreign Application Priority Data Feb. l4, I969 Japan 44/10486 [52] US. Cl. 260/954, 71/87 [5 l] Int. Cl. C07! 9/24, AOln 9/36 [58] Field ol Search 260/954 [56] References Cited UNITED STATES PATENTS 2,552,576 5/1951 Moyle 260/954 3,472,920 l0/l969 Schrader et al 260/954 Primary Examiner-Lewis Gotts Assistant Examiner-Anton H. Sutton Attorney-Burgess, Dinklage and Sprung [57] ABSTRACT N-alkyl-phosphoro-amido-thioates. i.e. O-(2- nitrophenyl)-O-alkyl-N-alkyl-phosphoro-amidothioates or O-(2-nitrophenyl)-O-alkyl-N-alkyl-amidothionophosphates, which possess herbicidal properties and which may be produced by conventional methods.

9 Claims, No Drawings N-ALKYL-PHOSPHORO-AMIDO-THIOATES The present invention relates to and has for its objects the provision for particular new N-alkylphosphoro-amido-thioates, i.e. O-(2-nitro-phenyl)-O- alkyl-N-alkyl-phosphoro-amido-thioates or O-( 2-nitrophenyl)-O-alkyl-N-alkyl-amido-thionophosphates, which possess herbicidal properties, active compositions in the form of mixtures of such compounds with solid and liquid dispersible carrier vehicles, and methods for producing such compounds and for using such compounds in a new way, especially for combating weeds, undesired plants, and the like, with other and further objects becoming apparent from a study of the within specification and accompanying examples.

It is already known that pent'achloro-phenol (A), which may be designated PCP, and 2,4-dichlorophenyl-4-nitro-phenyl-ether (B), which may be designated NIP as well as 2-chloro-4,6-bis (ethylamine)- l,3,5-triazine (C), which may be designated CAT or Simazin, possess herbicidal properties.

It is furthermore known from British Patent No. 659,682 that amido-thionophosphoric acid esters, generically, of the formula Y R S In which R is an alkyl or alkenyl radical, R is an alkyl radical, R is an alkyl radical or a hydrogen atom, and one Y is a nitro radical and the other y is a hydrogen atom or a nitro radical, possess insecticidal and fungicidal properties. In said British Patent, it is indicated only that such compounds have insecticidal and acaricidal activity as well as activity for the control of harmful fungi on plants, and that they can be used in the form of spray preparations. However, there is no actual test data showing their efficacy, and no indication that such compounds might have herbicidal activity. Furthermore, no mention is made of the applicability of such compounds to soil or of any reason to expect them to have herbicidal activity. I

On the other hand, U.S. Pat. No. 3,074,790 describes compounds, for example O-(2,4-dichloro-phenyl)-O- methyl-N-isopropyl-phosphoro-amido-thioate (D), which have herbicidal properties.

It hasnow been found, in accordance with the present invention, that the particular new N-alkyl phosphoro-amido-thioates, i.e. O-(2-nitro-phenyl)-O- alkyl-N-alkyl-phosphoro-amido-thioates, of the formula R S N02 in which R is alkyl of one to three carbon atoms, and

R is alkyl of four to five carbon atoms, exhibit strong herbicidal, especially selective herbicidal, properties.

It has been furthermore found, in accordance with the present invention, that the particular new compounds of formula 1 above may be produced by the process which comprises reacting an O-alkyl-N-alkylamido-thiono-phosphoric acid ester halide of the formula RZNH in which R and R are the same as defined above, and Hal is a halogen atom such as chloro, bromo, iodo or fluoro, especially chloro, with a 2-nitro-phenol, preferably in the presence of an acid binding agent, or with a salt of Z-nitro-phenol, correspondingly of the formula (III) in which M is hydrogen, or a cation such as an ammonium or alkali metal cation, for example potassium, sodium, and the like.

Surprisingly, the particular new compounds of formula 1 above according to the present invention show both a higher and a more specific herbicidal effectiveness than the previously known compounds which are known to be usuable for such purposes, such as compounds (A), (B) and (C) noted above. Such herbicidal effectivenss would not have been appreciated on the basis of the generic disclosure of related compounds for remote purposes in British Pat. No. 659,682. The instant compounds are especially effective as preemergence herbicides, and exhibit a remarkable effect in killing weeds, with only slight, if any, phytotoxic effect toward cultivated plants such as rice. The instant compounds therefore'represent a valuable contribution to the art.

Advantageously, in accordance with the present invention, in the various formulae herein:

R represents straight and branched chain lower alkyl hydrocarbon of one to three carbon atoms such as methyl, ethyl, nand iso-propyl, and the like, especially C, alkyl; and

R represents Straight and branched chain alkyl hydrocarbon of 4-5 carbon atoms such as n-, iso-, sec.- and tert.-butyl, n-and iso-amyl, and the like, especially branched C alkyl, and more especially branched C alkyl.

Preferably, R is C alkyl and R is branched C alkyl.

In particular, R is C alkyl and R is branched C alkyl.

Alternatively, in particular, R is C alkyl and R is isoor sec.-butyl or iso-pentyl.

The reaction course according to the instant production process is illustrated by the following formula scheme:

N02 R s \ll P-Hal MO RZNH (II) (III) N02 R O\fi P-O MHal RZNH in which R, R Hal and M are the same as defined above.

The starting materials which may be used for the instant production process are clearly characterized by formulae ll and Ill above, and are well known or can be readily prepared.

Advantageously, the instant active compounds exhibit a strong herbicidal potency and can therefore be used as gemination inhibiting agents or weed-killers. By weeds in the sense used herein are meant all plants which grow in places where they are not desired. Whether the active compounds according to the present invention act as total or selective herbicidal agents depends on the amount applied, as the artisan will appreciate.

The active compounds according to the present invention can be used for example in the case of the following plants: dicotyledons, such as mustard (Sinapis), cress (Lepidium), catch weed (Galium), common chickweed (Stellaria), camomile (Matricaria), French weed (Galinsoga), goose-foot (Chenopodium), stinging nettle (Urtica), groundsel (Senecio), wild amaranth (Amaranthus), common purslane (Portulaca), cotton (Gossypium), beets (Beta), carrots (Daucus), beans (Phaseolus), potatoes (Solanum), coffee (Coffea), cabbage (Brassica), spinach (Spinacia), cucumber (Cucumis), tomato (Lycopersicum), japanese radish (Raphanus); monocotyledons, such as timothy (Phleum), meadowgrass (Poa), fescue (Festuca), finger grass (Digitaria), goosegrass (Eleusine), green foxtail (Setaria), raygrass (Lolium), cheat (Bromus), barnyard grass (Echinochloa), maize (Zea), rice (Oryza), oats (Avena), barley (Hordeum), wheat (Triticum), millet (Panicum) and sugar cane (Saccharum); spikerush (Eleocharis) etc; and the like.

The instant compounds are preferably used as selective herbicides and especially when applied to soil before germination, although they exhibit a particularly good selectivity when applied before and after emergence, e. g. in upland and paddy fields. The instant compounds have an excellent controlling action on weeds in paddy fields.

Significantly, the active compounds of the present invention are distinguished by the fact that they have little or no phytotoxicity to rice plants or other cultivated plants although they are markedly effective in small dosages as compared with PCP and NIP, i.e. compounds (A) and (B), etc. which have hitherto been used widely as herbicides in paddy fields. Furthermore, the same effect as with CAT or Simazin, i.e. compound (C), is generally achievable using the instant active compounds without any harm to crops, e.g. when applied to soil before germination for controlling weeds in upland fields. Especially when applied to soil before germination, the instant compounds are far better than the already known herbicides in that such instant compounds show a superior selective herbicidal'activity, depending on the amount applied, with little or no phytotoxicity to cultivated plants.

Surprisingly, those compounds of formula I above in which R is branched alkyl of four carbon atoms are particularly effective against weeds in paddy fields, weeds of the Graminae family, broad-leaved weeds and perennial weeds, and are much more active and effective than those in which the corresponding R radical has less than four carbon atoms.

The active compounds according to the present invention significantly also show a secondary insecticidal and fungicidal activity, e.g. against insects and phytopathogenic fungi which infest plants.

The active compounds according to the instant invention can be utilized, if desired, in the form of the usual formulation or compositions with conventional inert (i.e. plant compatible or herbicidally inert) pesticide diluents or extenders, i.e. diluents or extenders of the type usuable in conventional pesticide formulations or compositions, e.g. conventional pesticide dispesible carrier vehicles, such as solutions, emulsions, suspensions, emulsifiable concentrates, spray powders, pastes, soluble powders, dusting agents, granules, etc. These are prepared in known manner, for instance by extending the active compounds with conventional pesticide dispersible liquid diluent carriers and/or dispersible solid carriers optionally with the use of carrier vehicle assistants, e.g. conventional pesticide surface-active agents, including emulsifying agents and/or dispersing agents, whereby, for example, in the case where water is used as diluent, organic solvents may be added as auxiliary solvents. The following may be chiefly considered for use as conventional carrier vehicles for this purpose: inert dispersible liquid diluent carriers including inert organic solvents, such as aromatic hydrocarbons (e.g. benzene, toluene, xylene, etc. halogenated, especially chlorinated, aromatic hydrocarbons (e.g. chloro-benzenes), paraffms (e.g. petroleum fractions), chlorinated aliphatic hydrocarbons (e.g. methylene chloride, etc.), alcohols (e.g. methanol, ethanol, propanol, butanol, etc., ethers, ether-alcohols (e.g. glycol monomethyl ether, etc.), amines (e.g. ethanol-amine, etc.), amides (e.g. dimethyl formamide, etc.), sulfoxides (e.g. dimethyl sulfoxide, etc.), ketones (e.g. acetones, etc.), and/or water; as well as inert dispersible finely divided solid carriers, such as ground natural minerals (e.g. kaolins, alumina, silica, chalk, i.e. 'calcium carbonate, talc, kieselguhr, montmorillonite, clay, etc.), and ground synthetic minerals (e.g. highly dispersed silicic acid, silicates, e.g. alkali silicates, etc.); whereas the following may be chiefly considered for use as conventional carrier vehicle assistants, e.g.- surface-active agents, for this purpose: emulsifying agents,

such as non-ionic and/or anionic emulsifying agents (e.g. polyethylene oxide esters of fatty acids, polyethylene oxide ethers of fatty alcohols, alkyl sulfonates, aryl sulfonates, etc., and especially alkyl aryl-polyglycol ethers, magnesium stearate, sodium oleate, etc.); and- /or dispersing agents, such as lignin, sulfite waste liquors, methyl cellulose, etc.

active agents, especially plant protection agents, such as other herbicides, or fungicides, insecticides, acaricides, nematocides, bactericides, plant growth regulators, soil disinfectants, Spreaders, wetting agents, adhesive agents, etc., including phenoxy compounds, chlorophenol compounds, carbamates, diphenyl ethers, urea compounds, triazine compounds, and other known agricultural chemicals and/or fertilizers, etc., if desired, or in the form of particular dosage preparations for specific application made therefrom, such as solutions, emulsions, suspensions, powders, pastes, and granules which are thus ready for use. Mixed application, especially with phenoxy herbicides, for example esters of MCP, i.e. 2-methyl-4-chloro-phenoxy acetic acid, is effective and gives rise to synergistic effects.

As concerns commercially marketed preparations, these generally contemplate carrier composition mixtures in which the active compound is present in an amount substantially between about 0.1 and 95 percent by weight, and preferably 0.5 and 90 percent by weight, of the mixture, whereas carrier composition mixtures suitable for direct application or field application generally contemplate those in which the active compound is present in an amount substantially between about 0.005l percent, preferably 0.008- percent, by weight of the mixture. Thus, the present invention contemplates over-all compositions which comprise mixtures of a conventional dispersible carrier vehicle such as (l) a dispersible inert finely divided carrier solid, and/or (2) a dispersible carrier liquid such as an inert organic solvent and/or water preferably including a surface-active effective amount of a carrier vehicle assistant, e.g. a surface-active agent, such as an emulsifying agent and/or a dispersing agent, and an amount of the active compound which is effective for the purpose in question and which is generally between about 0.005-95 percent, and preferably 0.008-95 percent, by weight of the mixture.

In particular, the amount of active compound applied per unit area varies according to the purpose intended, i.e. the effect desired, and the mode of application. In general, higher quantities of substantially between about 5-40 kg, of active compound per hectare are ap plied for total or non-selective herbicidal activity, whereas lower quantities of substantially between about l.25-5 kg of active compound per hectare are applied for selective herbicidal activity, although such active compound may be applied generally in amounts of 125-40 kg per hectare, i.e. irrespective of the presence or absence of the carrier vehicle. Essentially, the active compounds according to the present invention tend to show non-selective or total herbicidal action when used in an amount of more than 5kg per hectare, e.g. 5-40 kg/ha, whereas such compounds tend to show selective herbicidal action, especially for weeds as opposed to valuable cultivated crops such as rice, when used in smaller appropriate amounts, e.g. 1-4 or 1.25-5 kg/ha,i.e. irrespective of the presence or absence of the carrier vehicle.

The active compounds can also be used in accordance with the well-known ultra-low-volume process with good success, i.e. by applying such compound if normally a liquid, or by applying a liquid composition containing the same, via very effective atomizing equipment, in finely divided form, e.g. average particle diameter of from 50-100 microns, or even less, i.e. mist form, for example by airplane crop spraying techniques. Only up to at most about a few liters/hectare are needed, and often amounts only up to about 1 quart/acre, preferably 2-16 fluid ounces/acre, are sufficient. In this process it is possible to use highly concentrated liquid compositions with said liquid carrier vehicles containing from about 20 to about percent by weight of the active compound or even the percent active substance along, e.g. about 20-100 percent by weight of the active compound.

While the active compounds can be used particularly effectively according to the pre-emergence method, they are also effective when used according to the postemergence method.

Especially when application is carried out mainly before the germination of cultivated plants, the general conditions of cultivation are not so important, but the quantity of active compound to be applied per unit area and the application method are important, as the artisan will appreciate.

Furthermore, the present invention contemplates methods of selectively killing, combatting or controlling undesired plants, e.g. weeds and the like, which comprise applying to at least one of (a) such weeds and (b) their habitat, i.e. the locus to be protected, a herbicidally effective or toxic amount of the particular compound of the invention alone or together with a carrier vehicle as noted above. The instant formulations or compositions are applied in the usual manner, for example by spraying, atomizing, scattering, dusting, watering, sprinkling, and the like, whether for preemergence application to the soil or post-emergence application to the weeds.

It will be realized, of course, that in connection with the pre-emergence use of the instant compounds as well as the post-emergence use thereof, the concentration of the particular active compound utilized in admixture with the carrier vehicle will depend upon the intended application and may be varied within a fairly wide range depending upon the weather conditions, the soil, the purpose for which the active compound is used', e.g. for total oronly selective herbicidal effect, and the plants which are to be controlled or protected. Therefore, in special cases, it is possible to go above or below the aforementioned concentration ranges and ranges of amountsper unit area.

The following illustrate, without limitation, examples of formulations which may be used in accordance with the present invention.

Formulation A 5 percent by weight of instant compound (I), and 95 percent by weight of a mixture of talc and clay (3:1) are formulated into a dust by mixing and crushing, and applied by dusting as such to weeds and/or their habitat.

Formulation B 20 percent by weight of instant compound (2), 75 percent by weight of a mixture of talc and clay (3:2), 3 percent by weight of sodium alkylbenzene sulfonate, and 2 percent by weight of sodium dinaphthylmethane disulfonate are formulated into a wettable powder by mixing and crushing, and applied diluted with water at the concentration of l to 500 by spraying to weeds and- /or their habitat.

Formulation C 20 percent by weight of instant compound (3), 75 percent by weight of xylol, and percent by weight of the emulsifier Sorpol (trade name of the product of Toho Kagaku K.K., Japan: polyoxyethylenealkylarylether) are formulated into an emulsifiable concentrate by mixing and stirring, and applied diluted with water at the concentration of l to 1,000 by spraying to weeds and/or their habitat.

Formulation D Instant compound (2) is dissolved in xylol, and the solution is sprayed onto clay granules while rotating and mixing so that about percent by weight of the active compound is contained thereon. The granular formulation is applied as such by scattering on the surface of soil.

Formulation E 3 percent by weight of instant compound (2), 1.5 percent by weight of the ethyl ester of MCP, i.e. 2-methyl-4-chloro-phenoxy acetic acid, and 95.5 percent by weight of bentonite are mixed together. Such mixture containing 10 percent water is granulated. The granular formulation is applied as such by scattering on the soil surface of paddy fields.

The herbicidal effectiveness of the particular new compounds of the present invention is illustrated, without limitation, by the following Examples.

Example 1 Test against weeds of paddy fields Preparation of active compounds:

Carrier vehicle 5 pans by weight of acetone or 5 parts by weight of tale 1 part by weight of benzyloxypolyglycolether To produce a suitable preparation of the particular active compound, 1 part by weight of such active compound is throughly mixed with either one of the stated amounts of carrier vehicle and the stated amount of emulsifier. A resulted emulsifiable concentrate or a wettable powder is then diluted with water to a desired final concentration.

Test method:

Pots of l/5,000 a. are charged with paddy field soil and then filled with water. Paddy rice seedlings (Kinmaze variety) of 3 to 4 leaves stage are transplanted into the pots under irrigated conditions. After the seedlings have taken root, seeds of barnyardgrass and broad-leaved weeds are sown and spikerush are planted in such pots simultaneously.

The preparations of the given active compound are sprayed at the rate of 500, 250 and 125 g of active compound per 10 a. of pot soil. After 3 weeks, the herbicidal effect against the barnyardgrass, spikerush and broad-leaved weeds and the phytotoxicity to the paddy rice are determined in accordance with the following scale.

Phytotoxicity 5 Plants are completely dead 4 Remarkable damage 3 Marked damage 2 Small damage germinated 2 Plants are markedly damaged or or less germinated l Plants are slightly damaged or or less germinated l Slight damage 0 No phytotoxieity Herbicidal effect against weeds of paddy fields and phytotoxicity to rice Active Amount Compound of active Herbicidal effect Phyto- No. compound bamtoxicity in g/ l0 a. yardspikebroadgrass rush leaved rice weeds Compounds of invention 500 5 5 5 0 1,) 250 5 5 5 0 l25 5 4 5 0 500 5 5 5 0 (2,) 250 5 5 5 0 l25 5 4-5 5 0 500 5 5 5 0 (3 250 5 5 5 0 I25 5 4 4-5 0 500 5 5 5 0 (4,) 250 5 4 4 0 l25 4 3 4 0 9Q 5 5 5 0 1) 250 5 5 5 0 l 25 5 4-5 5 0 Known Compounds- Comparison (A) penta- 500 5 3 5 0 chloro phenol 250 3 0 2 0 l 0 0 0 (B) 2,4dichloro-phenyl- 500 5 5 5 3 4'-nitro- 250 5 5 5 1 phenyl ether 125 3 l 2 0 Control 0 0 0 0 NOTES:

1. Broad-leaved weeds are Monochoria vaginalis, Rotola indica, Lindemia pyxidaria, Dopatrium junceum, etc. 2. Compounds of invention have corresponding numbers to those in Table 3 below.

Example 2 Test against weeds of upland fields Preparation of the active compounds:

Carrier vehicle 5 parts by weight of acetone or 5 parts by weight of tale 1 part by weight of benzyloxy-polyglycolether To produce a suitable preparation of the particular active compound, 1 part by weight of such active compound is throughly mixed with either one of the stated amounts of carrier vehicle and the stated amount of emulsifier. A resulted emulsifiable concentrate or a wettable powder is then diluted with water to a desired final concentration.

germination or 90% or less germinated 1 Plants are slightly damaged after germination or 90% or more germinated No effect 0 No phytotoxicity EXAMPLE 3 sec.C4HnNH 3) 14 g (0.1 mol) of 2-nitro-phenol are dissolved in 100 ml of acetonitrile and 14 g of anhydrous potassium carbonate are added to the resulting solution. 21.6 g (0.1 mol) of O-ethyl-N-sec-butyl-amid0-thiono-phosphoric acid ester chloride are added dropwise thereto at C, with rigorous stirring. The mixture is further stirred at C for 5 hours to complete the reaction. The inorganic salt produced is filtered off and the filtrate distilled to remove the solvent. The residue is dissolved in ml of benzene and the benzene solution is washed with 1 percent aqueous solution of sodium carbonate, which has been dried over anhydrous sodium sulfate. After distilling off the benzene, 25.8 g of The particular active compounds tested and the re- O-(2-mtro-phenyl)-O-ethyl-N-sec.-butyl-phosphorosults obtained can be seen from the following Table 2. amido-thioate, an oily substance with the refractive TABLE 2 lllorblcldnl oll'ect against woods of upland fields and phytotoxlclty to various crops] IIcrblcidal cllcct Phytotoxicity Amount Barnynrd- Finger- Wild Common of active grass grass Dent amaranth purslane compound, (Echino- (Digifoxtail- (Amaran- (Portu- Upland Japanese Cucum- Active compound number g./10 a. chloa) taria) (Setaria) thus) laca) rice radish ber Tomato Carrot Compounds of invention:

(4,) 400 5 5 5 5 5 0 1 0 0 0 200 5 5 4 5 5 0 0 0 0 0 100 5 4 4 3-4 5 0 0 0 0 0 Known compounds com- 7 parison:

(C) 2'cl1loro-4,6-bis- (ethylamino)- 1,3, 6-trlazine 100 5 5 5 5 5 2 3 2 2 2 g I 50 4 4 5 5 5 0 l 1 l 1 (B) 2, 4-dlchlorophenyl-4-nltrov phenyl ether 400 5 5 5 5 5 3 1 5 5 5 200 5 5 4 5 5 0 O 2 2 3 Control 0 0 0 0 0 0 0 0 0 0 NOTE.-Compounds of invention have corresponding numbers to those in Table 3 below.

Compound number index n 1.5319, are obtained.

The following Table 3 illustrates appropriate data for typical compounds of the present invention.

TABLE 3 Structural formula ()-(Q-nltro-phonyl)-0-othyl-N- soc.-hutyl-phosplioro-amldotliioate.

TABLE 3--Continued It will be realized by the artisan that all of the foregoing compounds contemplated by the present invention possess the desired selective or total herbicidal proper ties, and especially the capability of selectively destroying weeds, as well as a comparatively low toxicity toward warm-blooded creatures and a concomitantly low phytotoxicity with respect to higher plants, depending upon the amount used, enabling such compounds to be used with correspondingly favorable compatibility with warm-blooded creatures and higher plants for more ef fective control and/or elimination of weeds by selective application of such compounds to such weeds and/or their habitat. Nevertheless, the instant compounds possess total herbicidal action when used in large quantities, although selective herbicidal action is obtained when used in smaller quantities. As contemplated herein, the term weeds" is meant to include not only weeds in the narrow sense, but also in the broad sense, whereby to cover all plants and vegetation considered undesirable for the particular purposes in question.

It will be appreciated that the instant specification and examples are set forth by way of illustration .and not limitation, and that various modifications and changes may be made without departing from the spirit and scope of the present invention which is to be limited only by the scope of the appended claims.

What is claimed is:

l. N-alkyl-phosphoro-amido-thioate of the formula R N H in which R is alkyl of one to three carbon atoms and R is alkyl of four to five carbon atoms.

2. Compound according to claim 1 wherein R is C alkyl and R is C branched alkyl.

3. Compound according to claim 1 wherein R is C alkyl and R is C branched alkyl.

4. Compound according to claim 1 wherein R is C alkyl and R is C, branched alkyl.

5. Compound according to claim 1 wherein R is C alkyl and R is selected from the group consisting of iso-butyl, sec.-butyl and iso-pentyl.

6. Compound according to claim 1 wherein such compound is O-(Z-nitro-phenyl)-O-methyl-N-sec.- butyl-phosphoro-amido-thioate of the formula CHJO S 7. Compound according to claim 1 wherein such compound is O-( Z-nitro-phenyl)-O-ethyl-N-sec.-butylphosphoro'amido-thioate of the formula NO: 021150 S P-O see-C lHiNH 8. Compound according to claim 1 wherein such compound is O-(2-nitro-phenyl)-O-ethyl-N-iso-butylphosphoro-amido-thioate of the formula compound is O-(2-nitro-phenyl)-O-ethyl-N-isopentylphosphoro-amido-thioate of the formula 

2. Compound according to claim 1 wherein R1 is C1-3 alkyl and R2 is C4-5 branched alkyl.
 3. Compound according to claim 1 wherein R1 is C1-2 alkyl and R2 is C4-5 branched alkyl.
 4. Compound according to claim 1 wherein R1 is C1-2 alkyl and R2 is C4 branched alkyl.
 5. Compound according to claim 1 wherein R1 is C1-2 alkyl and R2 is selected from the group consisting of iso-butyl, sec.-butyl and iso-pentyl.
 6. Compound according to claim 1 wherein such compound is O-(2-nitro-phenyl)-O-methyl-N-sec.-butyl-phosphoro-amido-thioate of the formula
 7. Compound according to claim 1 wherein such compound is O-(2-nitro-phenyl)-O-ethyl-N-sec.-butyl-phosphoro-amido-thioate of the formula
 8. Compound according to claim 1 wherein such compound is O-(2-nitro-phenyl)-O-ethyl-N-iso-butyl-phosphoro-amido-thioate of the formula
 9. Compound according to claim 1 wherein such compound is O-(2-nitro-phenyl)-O-ethyl-N-isopentyl-phosphoro-amido-thioate of the formula 